The invention relates to an electrophotographic image forming apparatus, and in particular, to a toner supply technology.
In a high-speed image forming apparatus or a color image forming apparatus, because the capacity of its toner reservoir unit for storing toner is large, there is a problem that it sometimes happens a case where it is difficult to dispose the toner reservoir unit in the neighborhood of the development device.
As regards means for solving such a problem, it has been developed a toner supply technology in which toner particles are conveyed from the toner reservoir unit to the development device by a toner conveyance method called an air conveyance method which is capable of conveying toner particles to a distant place (the publication of the unexamined patent applications H7-219329, H10-97130, H10-268641, and H10-299672).
The basic structure of a toner supply device using an air conveyance method is composed of a toner reservoir unit, a fluid conveyance means for conveying a mix fluid of toner and air from the toner reservoir unit, and a toner separation unit for separating toner particles from the conveyed mix fluid.
An electrophotographic image forming apparatus used as a copying machine or the like is generally composed of an image forming section for forming a toner image on a photoreceptor and transferring the toner image onto a recording sheet, a recording sheet accommodation section for accommodating recording sheets, and a sheet feed section for conveying a recording sheet from the recording sheet accommodation section to the image forming section, and the sheet feed section is disposed on one side of the recording sheet accommodation section.
In an image forming apparatus described in the publication of the unexamined patent applications H7-219329, H10-97130, H10-268641, and H10-299672, a toner supply section for supplying toner to be supplied to the development means of the image forming section is disposed on the same side as the sheet feed section with respect to the recording sheet accommodation section.
Because of the arrangement of the above-mentioned sheet feed section, there is little extra space at the side part of the above-mentioned recording sheet accommodation section where the above-mentioned sheet feed section is disposed; therefore, a toner reservoir unit is disposed, for example, in the upper part of the image forming apparatus. However, because the toner reservoir unit cannot be made large-sized enough, there is a problem that it is impossible to provide a toner reservoir unit having a toner accommodation capacity adapted to the high-speed performance of the image forming apparatus.
In the publication of the unexamined patent application H10-268641, a toner reservoir unit separately provided outside the image forming apparatus is disclosed. However, it is not desirable to provide a toner reservoir unit separately because it makes larger the installation area occupied by the image forming apparatus. Further, it raises a problem that it makes difficult the addition of an attachment apparatus such as a recording sheet accommodation apparatus or a finisher apparatus.
Further, in the publication of the unexamined patent application H11-212348, a toner reservoir unit is disposed sideward of sheet feed units, and so-called “Mono pump” is employed as a pump for conveying a toner. On the other hand, in the present application, two diaphragm type pumps are employed, one for supplying a toner and the other for collecting the toner. A toner separation section is disposed upward of a developing device.
In addition, in the publication of the unexamined patent application 2000-137376, a toner reservoir section is disposed upward of a sheet feeding section and on a side of sheet conveyance section, which is different in position from that of the present application.
Furthermore, in the publication of the unexamined patent application 2000-296772, a toner reservoir unit is disposed sideward of sheet feed units, and a toner is conveyed by air after the toner is conveyed by a screw from the toner reservoir unit. One pump is employed for conveying the toner. In contrast, in the present application, a toner is directly conveyed by air from a toner reservoir unit. As explained above, two pumps are employed for supplying and collecting the toner, respectively. In addition, the image forming apparatus of the present application is further provided with a toner separation section.